Forging press

ABSTRACT

A forging press includes a forging chamber into which a forging cylinder can be pressed. The forging cylinder is integral with a main piston arranged in a working cylinder to which pressure fluid can be supplied. The forging piston is slidable within an annular member which is fixed in an axially slidable sleeve, and which can be moved by pressure fluid supplied to either end thereof. Within the main piston is a pressure-equalizing chamber, into which fits a stationary back-pressure piston. Passages are provided connecting the pressure equalizing chamber with the forging chamber. The cross-section of the back-pressure piston is less than that of the forging piston. In the bottom part of the forging chamber there is arranged a groove which connects with a discharge passage. When pressure fluid is applied to the sleeve, it moves downwardly and the annular member engages the bottom of the forging chamber and closes the outlet groove so as to prevent the escape of fluid therefrom. Pressure in the main cylinder then pushes down the forging piston. As the cross-section area of the back-pressure piston is smaller than that of the forging piston, the increase in volume of the pressure-equalizing chamber will not be as great as the decrease in volume of the forging chamber. This in turn leads to an increase in pressure in both chambers. The relation between the cross-section areas of the back-pressure piston and the forging piston is chosen so that a suitable pressure increase is obtained in the chambers.

United States Patent 1191 Claesson Mar. 18, 19 75 FORGING PRESS [75]Inventor: Harry Claesson, Vasteras, Sweden [73] Assignee: AllmannaSvenska Elektriska Aktiebolaget, Vasteras, Sweden [22] Filed: Apr. 22,1974 [21] Appl. No.2 463,039

[30] Foreign Application Priority Data May 3, 1973 Sweden 7306177 [52]US. Cl. 72/60, 72/453 [51] Int. Cl B2lj 9/02 [58] Field of Search 72/60,453; 352, 358, 57,

[56] References Cited UNITED STATES PATENTS 3,383,891 5/1968 Geitz 72/573,415,088 12/1968 Alexander 72/60 3,686,910 8/1972 Fuchs 72/60 3,707,864l/l973 Pigott 72/60 FOREIGN PATENTS OR APPLICATIONS 1,195,826 6/1970lJnitedKingdorn 72/377 Primary Examiner-C. W. Lanham AssistantExaminerGene P. Crosby [57] ABSTRACT A forging press includes a forgingchamber into which a forging cylinder can be pressed. The forgingcylinder is integral with a'main piston arranged in a working cylinderto which pressure fluid can be supplied. The forging piston is slidablewithin an annular member which is fixed in an axially slidable sleeve,and which can be moved by pressure fluid supplied to either end thereof.Within the main piston is a pressureequalizing chamber, into which fitsa stationary backpressure piston. Passages are provided connecting thepressure equalizing chamber with the forging chamber. The cross-sectionof the back-pressure piston is less than that of the forging piston. inthe bottom part of the forging chamber there is arranged a groove whichconnects with a discharge passage. When pressure fluid is applied to thesleeve, it moves downwardly and the annular member engages the bottom ofthe forging chamber and closes the outlet groove so as to prevent theescape of fluid therefrom. Pressure in the main cylinder then pushesdown the forging piston. As the cross-section area of the back-pressurepiston is smaller than that of the forging piston, the increase involume of the pressure-equalizing chamber will not be as great as thedecrease in volume of the forging chamber. This in turn leads to anincrease in pressure in both chambers. The relation between thecross-section areas of the back-pressure piston and the forging pistonis chosen so that a suitable pressure increase is obtained in thechambers.

9 Claims, 6 Drawing Figures p p p F ORGING PRESS BACKGROUND OF THEINVENTION 1. Field of the Invention The invention relates to a forgingpress operated by pressure fluid.

2. The Prior Art During forging operations in presses where a greatreduction of the forged billet isrequired or where the material in thebillet is very brittle, it is impossible to employ conventional methodswithout encountering difficulties, for example the formation of cracksat the edges of the billet. One way of avoiding this is to forge thebillet in a high-pressure chamber where the free surfaces of the billetare subjected to a hydrostatic pressure of a few kilobars. One known wayof forging in this manner is to have the forging chamber in the form ofa cylinder into which thebillet to be forged is inserted. The cylinderis then filled with oil and the forging piston acting as a punch isinserted into the opening of the cylinder. As the forging piston isinserted into the cylinder, the pressure in the cylinder increasesradpidly, and, in order that the pressure should not be too high; it isnecessary to drain off oil from the chamber. This draining is performedthrough a reduction valve which is adjusted so that the desired pressureis obtained in the forging chamber. Forging is performed by the factthat the punch or the forging piston hits the billet and compresses it,while at the same time the billet receives a support pressure from theoil on the surfaces which are not supported by the punch and the bottomof the cylinder, respectively. The forging itself can of course besatisfactorily carried out in this way, but a serious drawback of thisprocedure is that reduction valves used in this system are rapidly wornout and must be replaced at frequent intervals. Another drawback is thata loss of power naturally occurs in the reduction valve.

SUMMARY OF THE INVENTION The present invention relates to a forgingpress which is not subject to these drawbacks. The forging press isprovided with a pressure chamber into which a back pressure piston witha smaller piston area than the forging piston can be inserted in asealing'manner. A connection is provided between the pressure-equalizingchamber and the forging chamber. The pressureequalizing chamber with itsback pressure piston is arranged so that its volume is increased whenthe forging piston is inserted into the forging chamber, thus decreasingthe volume of the forging chamber. Because the piston area of the backpressure piston is smaller than the piston area of the forging piston,an increase in pressure in the forging chamber is obtained in thisoperation. This increase in pressure can be calculated in advance bychoosing a suitable ratio between the respective piston areas inrelation to the volumes of the rest of the chambers. A forging press inaccordance with the embodiment described consequently does not have tobe provided with a reduction valve at the outlet from the forgingchamber. When the forging piston reaches the billet and seals againstit, an additional force is also obtained in the forging pressure whichcorresponds to the oil pressure on a surface corresponding to thecontact surface between the billet and the punch.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is best understood withreference to the accompanying drawings wherein:

FIG. 1 shows the forging press in cross-section.

FIGS. 2-6 show the positions of the various pistons in cross-section atvarious stages of the work cycle of the forging press.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, l designates a framewhich is suitably wound with steel strips. In the frame a forging tool 2is arranged. The forging tool 2 has a forging chamber 3 into which aforging piston 4 is sealingly insertable for the forging of a billet 5positioned in the forging chamber 3. Furthermore, the forging tool 2 isprovided with an annular maincylinder 6 in which a main piston 7 moves.In the main piston 7 there is arranged a pressure-equalizing chamber 8.A back-pressure piston 9, which is connected to the frame 1 and is thusstationary during a working cycle of the tool, is sealingly insertableinto the pressure-equalizing chamber 8. The channels 10 and 11 connectthe forging chamber 3 with the pressure-equalizing chamber 8 and arearranged in the main piston 7.

The walls of the forging chamber 3 are formed by a tubular member 12.This tubular member 12 is movable along its central axis. It isconnected to an outer, axially movable jacket 13. At the top this jacket13 fits slidingly into an annular slot 14 in the main piston 7. At thebottom it fits slidingly into a corresponding annular slot 15 providedin the bottom piece 16 of the forging tool 2. The ends of the jacket 13thus act as pistons in the respective annular slots 14 and 15.

For operation of the jacket 13 pressure oil can be transferred by meansof a pump 17 either through a conduit 18 to the slot 15 or through aconduit 19 to the slot14. The oil is pumped from the container 20 andthe switching between the different conduits l8 and 19 is performed bymeans of the valve 21.

Supply of oil to the pressure-equalizing chamber 8 is also performedfrom the container 20 by way of the pump 22, the valve 23 and theconduit 24, which opens out in the channel 25 which, in turn, opens outinto the pressure-equalizing chamber 8. In the conduit 24 a check valve26 is arranged, which prevents the oil from flowing from the backpressure chamber 8 back into the container 20. When switching the valve23, the conduit 24 is disengaged from the pump 22 which is now connecteddirectly to the return pipe 27.

The main piston is operated by pumping oil from the container 20 by wayof the pump 28, the valve 29, the conduit 30 and the channel 31 to themain cylinder 6. Emptying of the main cylinder 6 is performed byreversing the valve 29, the conduit 30 thus being connected to the openreturn pipe 33 and the pump 28 to the return pipe 32.

Outside the forging chamber there is a drain groove 34 which is in openconnection with the oil container 20 by way'of a channel 35 and aconduit 36.

Finally, between the tubular member 12 and the main piston 7 there is aspacing member 37.

The forging press operates in the following manner. FIG. 1 shows theforging tool 2 in the starting position for pressing. This means thatthe tubular slot 15 is under pressure because the pump 17 is pumping oilto the slot 15. On the other hand, the annular slot 14 communicatesfreely with the oil container. The main piston 7 is'supported by thespacing members 37 on the tubular member 12, which in turn is connectedto the jacket 13 which, in the starting position, is in its upperposition because of the oil pressure in the slot 15.

Further, the oil pressure is zero in the pressureequalizing chamber 8and the main cylinder 6 because these are in free connection with theoil container 20.

With the forging tool in this position the billet is placed into theforging chamber.

FIG. 2 shows the next stage in the working cycle. Here the annular slot15 has been brought into free connection with the oil container by theswitching of the valve 21, and at the same time the slot 14 has beenpressurized. This has caused the jacket 13 with its tubular member 12 tochange its position and it is now located in its lower end position. Inthis way the forging chamber is sealed off from the draining groove 34and a pressure-tight space is formed by the bottom piece 16, the member12 and the forging piston 4, disregarding the connection of the spacewith the pressureequalizing chamber 8 by way of channels 10 and 11.

With the tool in this position, the valve 23 is switched so that thepump 22, instead of pumping oil back to the container through the returnpipe 38, now pumps oil through the conduit 24 to the pressure-equalizingchamber 8 and the forging chamber 3.

After the forging chamber 3 has been filled with oil, the next phase inthe working cycle begins, as shown in FIG. 3. Here the valve 29 has nowalso been switched so that the pump 28 forces oil through the conduit 30to the main cylinder 6. This causes the main piston 7 to be drivendownward, the forging piston 4 being pressed into the forging chamber 3,the volume of which decreases. At the same time the volume of thepressure-equalizing chamber 8 increases, and oil flows from the forgingchamber 3 over to the pressureequalizing chamber 8 through the channels10 and 11. However, the piston area of the back-pressure piston 9 issmaller than the piston area of the forging piston 4, which means thenthe increase in volume of the chamber 8 will not be as great as thedecrease in volume of the forging chamber 3. This, in turn, will ofcourse lead to an increase in pressure in both chambers 8 and 3. Therelation between the areas of the different pistons is adjusted so thata suitable pressure increase, for example up to 4 kilobars, is obtainedin the forging chamher. The pressure increase can also be adjusted ifone does not start filling oil into the forging chamber 3 until theforging piston 4 has been pushed somewhat into the forging chamber 3.This results in the transfer of a smaller volume of oil from the forgingchamber to the pressure-equalizing chamber, which, in turn, of courseleads to a somewhat smaller increase in pressure at the same ratiobetween the piston areas in the different cases.

FIG. 4 shows the forging proper. It should be pointed out that, when theforging piston 4 hits the surface of the billet 5, an'additionalpressure is obtained in the forging pressure, which corresponds to theoil pressure on a surface corresponding to the contact surface betweenthe billet 5 and the forging piston 4. In FIG. 5 the forging process iscompleted and'the valve 29 has been switched so that the main cylinder 6has been brought into free connection with the container 20. Under highpressure in the forging chamber 3 and the pressureequalizing chamber'8,the oil then tends to increase the volume, resulting in an upwardpressure on the main piston 7. To be able to lift the main piston 7 toits upper position, however, further oil must also be pumped into theslot 14. This results in a complete decompression of the oil in theforging chamber 3 which can now be opened. 7

In FIG. 6, finally, the pump 17 has been connected to the slot 15, thejacket 13 with the tubular member 12 being raised to its upper position.The main piston 7 again is supported by the spacing members 37 on themember 12. As the tubular member 12 is lifted from the bottom piece 16,the oil in the forging chamber 3 is able to run out through the draininggroove 34 and the channel 35 down into the container 20. With theforging tool 2 in this position, the billet 5 which has now been forgedcan be removed from the tool.

It should be added that the degree of the increase in volume in theforging chamber 3 and the pressureequalizing chamber 8 together can beeasily adjusted to the compressibility of the pressure fluid, when theforging is being carried out, by choosing a suitable starting positionfor the forging piston 4.

Furthermore, the mechanical guiding of the forging piston 4 has a veryappropriate design, which contributes to causing the upper and lowerforging tools to meet each other with good precision. The guiding of theforging piston 4 is performed against the tubular member 12, which inturn is guided by the jacket 13.

I claim:

1. Forging press comprising a forging chamber (3), a forging piston (4)sealingly insertable into the forging chamber (3) for forging billets(5) arranged in the forging chamber (3), a main cylinder (6) and a mainpiston (7) arranged in the main cylinder (6) for imparting movement tosaid forging piston (4), means for filling said forging chamber (3) withoil which is compressed when the forging piston (4) forces its way intothe forging chamber (3), a pressure-equalizing chamber (8), meansconnecting the forging chamber (3) with the pressure-equalizing chamber(8), a bacl -pressure piston (9) with a smaller piston area than theforging piston (4) sealingly insertable into the pressure-equalizingchamber (8) and the main piston (7) being operatively connected to theforging piston (4) to effect a change in the volume of the forgingchamber (3) and the pressure-equalizing chamber (8), respectively, thevolume of the pressure-equalizing chamber (8) thereby increasing whenthat of the forging chamber (3) decreases.

2. Forging press according to claim 1, in which the back-pressure piston(9) is stationary and the pressureequalizing chamber (8) is arranged inthe main piston (7).

3. Forging press according to claim 1, in which the peripheral wall ofthe forging chamber (3) consists of an annular member (12), in one endof which the forging piston (4) is sealingly slidable.

4. forging means according to claim 3, in which the annular member (12)is displaceable axially.

5. Forging press according to claim 3, having an outer, axially movablejacket (13) surrounding and secured to the annular member (12), andmeans to move the jacket (13) axially.

6. Forging press according to claim 5 having outlet means (35) from theforging chamber and means conconnecting means between the forgingchamber (3) and the pressure-equalizing chamber (8) consists of means(10,11) in the main piston (7).

9. Forging press according to claim 1, wherein a conduit (24).connecting the forging chamber (3) and-the pressure-equalizing chamber(8) connected thereto are connected to an oil container (20).

1. Forging press comprising a forging chamber (3), a forging piston (4)sealingly insertable into the forging chamber (3) for forging billets(5) arranged in the forging chamber (3), a main cylinder (6) and a mainpiston (7) arranged in the main cylinder (6) for imparting movement tosaid forging piston (4), means for filling said forging chamber (3) withoil which is compressed when the forging piston (4) forces its way intothe forging chamber (3), a pressure-equalizing chamber (8), meansconnecting the forging chamber (3) with the pressure-equalizing chamber(8), a back-pressure piston (9) with a smaller piston area than theforging piston (4) sealingly insertable into the pressureequalizingchamber (8) and the main piston (7) being operatively connected to theforging piston (4) to effect a change in the volume of the forgingchamber (3) and the pressure-equalizing chamber (8), respectively, thevolume of the pressure-equalizing chamber (8) thereby increasing whenthat of the forging chamber (3) decreases.
 2. Forging press according toclaim 1, in which the back-pressure piston (9) is stationary and thepressure-equalizing chamber (8) is arranged in the main piston (7). 3.Forging press according to claim 1, in which the peripheral wall of theforging chamber (3) consists of an annular member (12), in one end ofwhich the forging piston (4) is sealingly slidable.
 4. forging meansaccording to claim 3, in which the annular member (12) is displaceableaxially.
 5. Forging press according to claim 3, having an outer, axiallymovable jacket (13) surrounding and secured to the annular member (12),and means to move the jacket (13) axially.
 6. Forging press according toclaim 5 having outlet means (35) from the forging chamber and meansconnected with the annular member (12) to close said oil means. 7.Forging press according to claim 6, in which the outlet means comprisesa drain groove (34) communicating with the forging chamber (3) fordraining off oil present in the forging chamber into an oil containerwhen the forging chamber (3) is opened after a completed work cycle. 8.Forging press according to claim 1, in which the connecting meansbetween the forging chamber (3) and the pressure-equalizing chamber (8)consists of means (10,11) in the main piston (7).
 9. Forging pressaccording to claim 1, wherein a conduit (24) connecting the forgingchamber (3) and the pressure-equalizing chamber (8) connected theretoare connected to an oil container (20).